[Server-devel] [OLPC Networking] RSSI value questions

[Ryan Crawford Comeaux]

On Thu, Apr 3, 2008 at 8:55 PM, <david at lang.hm> wrote:

> On Thu, 3 Apr 2008, Michail Bletsas wrote:
>
>  Let's not forget that you need some fixed reference points.
> > In commercial systems, the locations of the access points are well
> > known.
> > In ad-hoc networks the best that you can hope for is a topological map.
> >
>
> the assumption was that the measurements are being done from fixed points.
> either the school server antenna locations, or the known locations of
> specific assistant laptops.
>
> without known locations you can't do much.
>
> David Lang
>

Suppose you have your initial fixed points with known locations (server
antennas and any standalone repeaters).  Wouldn't you be able to identify
"temporarily" stationary points that, after deducing their locations, could
be deemed additional "listening stations"?  Once a node is identified as
such, any additional measurements it provides can be deemed credible and
then used to determine the locations of less stationary nodes.

As David said, some commercial solutions require calibration by walking a
node around the premises.  I think this has been shown to be fairly accurate
for a single AP's coverage area without having to add additional APs to the
network.

Most of the comments have been along the lines of using single measurements
to identify distances of separation.  I think a better solution would be to
include the mesh's routing table, packet arrival times, etc. along with RSSI
measurements.  If you generate one or more likely maps from each and then
average them out, I suspect you'd get a fairly accurate estimation of where
everybody is.  Coupled with preloaded measurements from around the premises,
a viable solution seems likely.

Is the XS capable of installing/"pushing" applications onto XOs
automatically?  If so, that allows for a very easy way to let the XOs
participate in the process without bothering users, as well as distributing
some of the number-crunching to take make things easier for the XS app.

Am I displaying complete naivety here about everything involved or does any
of this stuff make sense to you guys?

-Crawford
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